1. Field of the Invention
The present invention relates to an image recording apparatus for recording on a recording medium.
2. Related Background Art
A prior art image recording apparatus is exemplified typically by a heat transfer type facsimile equipment using an ink sheet thereon. The equipment detects a width of loaded or mounted recording sheet to control a data recording width.
However, a width of the ink sheet has not been detected hitherto, thus bringing about the following disadvantage. That is, if a B4-sized recording sheet is mounted despite having mounted, for example, an A4-sized ink sheet, the equipment decides a recordable size as B4, and so comes into a recording operation. However, the ink sheet width actually covers only the A4-size, and thus an image is recorded only in an A4-size domain where the ink sheet is present, but the image cannot be recorded in a recording sheet domain where the ink sheet is not present.
On the other hand, in the case of multiprint recording system, the following problem may arise inevitably.
First, a heat transfer printer will be described before going into multiprint.
Generally, the heat transfer printer uses an ink sheet with a heat-soluble (heat-sublimable) ink applied on a base film, and heats the ink sheet selectively on a thermal head according to an image signal thereby transferring the dissolved (sublimated) ink onto a recording sheet to image recording. Generally, the ink sheet is that of having the ink transferred perfectly on the recording sheet whenever the image is recorded (or so-called one-time sheet), therefore it is necessary that the ink sheet be conveyed so long as will correspond to the recorded length after recording one character or one line, and an unused portion of the ink sheet positioned accurately for the next recording. Consequently, the ink sheet is used increasingly, and a running cost of the heat transfer printer trends high as compared with a normal printer operating for recording on a heat-sensitive paper.
To solve such problems, there is proposed a heat transfer printer for conveying a recording sheet and an ink sheet at a speed difference provided therebetween as disclosed in Japanese Laid-Open Patent Application No. 57-83471 and Japanese Laid-Open Patent Application No. 58-201686 and also Japanese Patent Publication No. 62-58917.
Here, an ink sheet ready for recording images more than one time (or so-called multiprint sheet) is known as the ink sheet available for lowering a running cost of the heat transfer printer. From using the ink sheet, a recording length L can be recorded continuously with a conveying length of the ink sheet conveyed after end of each image recording or during the image recording adjusted to be less than the length L (L/n: n&gt;1). Thus, a merit of the ink sheet becomes n times of the conventional one, and a reduction in running cost of the heat transfer printer can be expected. Such recording system is called multiprint hereinafter.
In such multiprint system, since a conveying speed of the ink sheet is lower than the conveying speed of a recording sheet, it is necessary that a speed difference be taken between a rotational speed of a platen for conveying the recording sheet and the conveying speed of the ink sheet. Where the recording sheet is present between the ink sheet and the platen, the ink sheet slides well against the recording sheet as a friction factor of the recording sheet is small, however, once the range in which the ink sheet comes in contact directly with the platen gets large, a trouble may arise on conveying the ink sheet as a friction factor of the platen is large. This may cause wrinkles, breakage or other failures on the ink sheet, and thus is capable of bringing about a defect of image recording and a deterioration in image quality.